1. Field of the Invention
The present invention relates generally to “manway” covers for access to enclosed spaces such as tanks, conduits, storage areas, heat exchanger tubes. Particularly, the present invention relates to mechanisms to assist in the removal of “manway” covers. More particularly, the present invention relates to mechanisms for handling the removal and installation of “manway” covers that are too heavy to be handled by an unaided individual.
2. Description of the Prior Art
Manway covers are typically large, heavy, metal plates that are bolted to an opening. For purposes of the present invention, the definition of “manway covers” expressly means any heavy covers or closures used on pressure vessels, vacuum vessels, atmospheric vessels, heat exchangers, heat exchanger channel covers, heat exchanger channels, heat exchanger bonnets, or any type of blanking plate and is not construed to be limited to only covers used on openings that are dimensionally-sized to allow passage of a man. The most common are circularly-shaped and mate to a flange by way of a plurality of bolts evenly spaced around the periphery of the opening. However, it should be understood that the heavy covers may be any shape. The defined manway covers typically provide access to enclosed spaces such as tanks, conduits, storage areas, transfer tubes, pressure vessels, vacuum vessels, atmospheric vessels, heat exchangers, heat exchanger channel covers, heat exchanger channels, heat exchanger bonnets, and the like.
Routine servicing and inspection requirements as well as other operating conditions necessitate periodic removal of these manway covers. In view of the typical location and weight of the manway covers, it is not a simple task to remove the cover or to re-install the same. Removal is currently accomplished with the use of hand operated davit swing arms, chain falls, ratchet hoists, and brute force. Except for davit swing arms, it is necessary during the removal process to lower the covers a distance to a level surface.
Various devices have been devised to facilitate manway cover removal and re-installation. U.S. Patent Application Publication 2005/0242051 (2005, Porebski et al.) discloses a removable cover support system having a base member and a securing mechanism slidably insertable through at least one of a cover flange hole of a cover assembly, a retaining sleeve connected to the securing base assembly, a swingarm assembly rotatably supported by the retaining sleeve, and a lifting mechanism connected to the swingarm assembly.
U.S. Pat. No. 4,519,519 (1985, Meuschke et al.) discloses a davit assembly that is connected with a transfer tube and a hatch cover to move the cover away. The davit assembly, which is a swingarm, is permanently attached to the outside of the transfer tube.
U.S. Pat. No. 4,297,072 (1981, Shah et al.) discloses a manway handling apparatus having a support arm pivotally mountable on equipment having elliptical manway access openings. The support arm when mounted is swingable toward and away from an access opening and carries a bearing block supporting bracket which is longitudinally adjustably positionable on the arm. The bearing block is vertically adjustably positionable in the bracket and slidably supports a shaft which is attachable to an elliptical cover. The shaft carries structure means which when actuated by turning of a crank handle is effective for tilting the cover and to facilitate its installation and removal.
U.S. Pat. No. 4,865,513 (1989, Norris) discloses a portable manway cover handling apparatus. A boom is mounted within a sleeve for longitudinal translation and the sleeve is hinged to a base plate that is securable by a C-clamp to a superstructure beam in front of a manway cover. A hydraulic actuator bears against the sleeve to adjust its elevation. A powered cable winch is joined to one end of the boom and its cable passes through the boom, which is hollow to the opposite end, and about a pulley to a fastener for attachment to an eye secured in the upper edge of the manway cover. A presser foot is hydraulically actuated to bear against the manway cover with the cable attached to the cover so that the bolts holding the cover in place can be removed. Guide pins are provided for installation in the mounting flange to pilot the cover into registration with the bolt holes when the cover is to be mounted rather than demounted.
The prior art devices suffer from various disadvantages. The swingarm devices are bulky and comprise multiple parts for removably attaching the assembly to the manway or the swingarms are permanently attached to the manway. Other devices are also large, bulky and complicated structures using a boom that requires the base plate of the device to be secured by a C-clamp to a superstructure beam.
Therefore, what is needed is a manway cover handling device that is compact and portable. What is also needed is a manway cover handling device that is easy to attach and remove from a manway only when the manway cover needs to be removed. What is further needed is a manway cover handling device that is relatively lightweight compared to prior art devices. What is still further needed is a manway cover handling device that is simple to assemble.